Strand composite having latent elasticity

ABSTRACT

A nonwoven composite that exhibits latent elastic properties is provided. The composite is formed from an elastic strand layer laminated to a nonwoven web facing. Latent elasticity may be imparted to the elastic strand layer through the combination of a thermoplastic elastomer and a polyolefin capable of forming semi-crystalline domains among the elastomeric chains. More specifically, the elastic strand layer may be stretched in one or more directions to orient the elastomer chains. Without intending to be limited by theory, the present inventors believe that the oriented state of the chains may be held in place by the relatively stiff semi-crystalline domains of the polyolefin. The stretched elastic strand layer may subsequently be relaxed and bonded to a nonwoven web facing to form the composite. The composite may be later activated (e.g., heated) to shrink the elastic strand layer and provide it with “latent” stretchability. For instance, the composite may be heated at or above the softening temperature of the polyolefin to soften the crystalline domains and allow the chains to return to their unoriented state. As a result of the present invention, the elastic strand layer may be extended and recover from its unoriented state.

BACKGROUND OF THE INVENTION

Elastic composites are commonly incorporated into products (e.g.,diapers, training pants, garments, etc.) to improve their ability tobetter fit the contours of the body. For example, the elastic compositemay be formed from elastic strands and one or more nonwoven web facings.The nonwoven web facing may be joined to the strands while in astretched condition so that the nonwoven web facing can gather betweenthe locations where it is bonded to the strands when they are relaxed.The resulting elastic composite is stretchable to the extent that thenonwoven web facing gathered between the bond locations allows theelastic strands to elongate. Examples of stretch bonded composites aredisclosed, for example, in U.S. Pat. No. 5,385,775 to Wright.Unfortunately, however, the stretchable nature of the composites maycause problems during the manufacturing process of the ultimateproducts. For example, the force required to unwind the rolledcomposites may at least partially extend the elastic composite while theelastic article is in tension. This partial extension of the stretchablecomposite can make it difficult to properly measure and position thedesired quantity of the elastic article in the final product.

As such, a need exists for materials that remain relatively inelasticprior to incorporation into a final product, but which achieve a certainlevel of elasticity after having been activated in the final product.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, a method offorming a nonwoven composite having latent elasticity is disclosed. Themethod comprises forming an elastic strand layer comprising a pluralityof elastic strands, wherein the elastic strand layer is formed from athermoplastic elastomer and semi-crystalline polyolefin. The elasticstrand layer is stretched in the machine direction at a stretch ratiofrom about 2.0 to about 8.0, thereby forming a stretched elastic strandlayer. The stretched elastic strand layer is allowed to relax to achievea relaxation percentage of about 10% or more. A nonwoven web facing islaminated to the relaxed elastic strand layer.

In accordance with another embodiment of the present invention, anonwoven composite having latent elasticity is disclosed. The compositecomprises an elastic strand layer laminated to a nonwoven web facing.The elastic strand layer comprises a plurality of elastic strands and isformed from at least one thermoplastic elastomer and at least onesemi-crystalline polyolefin. The semi-crystalline polyolefin constitutesfrom about 40 wt. % to about 95 wt. % of the elastic strand layer andthe thermoplastic elastomer constitutes from about 5 wt. % to about 60wt. % of the elastic strand layer. The composite exhibits a percentstrain of about 50% or less when subjected to a load of 2000 grams-forceper 3 inches wide in the machine direction prior to heat activation.

In accordance with still another embodiment of the present invention, amethod for forming an absorbent article is disclosed. The methodcomprises fastening a nonwoven composite, such as described above, toone or more components of the article. The nonwoven composite is heatedand allowed to retract, thereby increasing the stretchability of thecomposite.

Other features and aspects of the present invention are described inmore detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth more particularly in the remainder of the specification, whichmakes reference to the appended figures in which:

FIG. 1 schematically illustrates a method for forming a compositeaccording to one embodiment of the present invention;

FIG. 2 schematically illustrates a method for forming a compositeaccording to another embodiment of the present invention; and

FIG. 3 is a perspective view of a personal care product that may beformed in accordance with one embodiment of the present invention.

Repeat use of reference characters in the present specification anddrawings is intended to represent same or analogous features or elementsof the invention.

DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS Definitions

As used herein, the term “nonwoven web” generally refers to a web havinga structure of individual fibers or threads which are interlaid, but notin an identifiable manner as in a knitted fabric. Examples of suitablenonwoven fabrics or webs include, but are not limited to, meltblownwebs, spunbond webs, carded webs, etc. The basis weight of the nonwovenweb may generally vary, such as from about 0.1 grams per square meter(“gsm”) to 120 gsm, in some embodiments from about 0.5 gsm to about 70gsm, and in some embodiments, from about 1 gsm to about 35 gsm.

As used herein, the term “meltblown web” generally refers to a nonwovenweb that is formed by a process in which a molten thermoplastic materialis extruded through a plurality of fine, usually circular, diecapillaries as molten fibers into converging high velocity gas (e.g.air) streams that attenuate the fibers of molten thermoplastic materialto reduce their diameter, which may be to microfiber diameter.Thereafter, the meltblown fibers are carried by the high velocity gasstream and are deposited on a collecting surface to form a web ofrandomly dispersed meltblown fibers. Such a process is disclosed, forexample, in U.S. Pat. No. 3,849,241 to Butin, et al., which isincorporated herein in its entirety by reference thereto for allpurposes. Generally speaking, meltblown fibers may be microfibers thatare substantially continuous or discontinuous, generally smaller than 10microns in diameter, and generally tacky when deposited onto acollecting surface.

As used herein, the term “spunbond web” generally refers to a webcontaining small diameter substantially continuous fibers. The fibersare formed by extruding a molten thermoplastic material from a pluralityof fine, usually circular, capillaries of a spinnerette with thediameter of the extruded fibers then being rapidly reduced as by, forexample, eductive drawing and/or other well-known spunbondingmechanisms. The production of spunbond webs is described andillustrated, for example, in U.S. Pat. No. 4,340,563 to Appel, et al.,U.S. Pat. No. 3,692,618 to Dorschner. et al., U.S. Pat. No. 3,802,817 toMatsuki, et al., U.S. Pat. No. 3,338,992 to Kinney, U.S. Pat. No.3,341,394 to Kinney, U.S. Pat. No. 3,502,763 to Hartman, U.S. Pat. No.3,502,538 to Levy, U.S. Pat. No. 3,542,615 to Dobo, et al., and U.S.Pat. No. 5,382,400 to Pike, et al., which are incorporated herein intheir entirety by reference thereto for all purposes. Spunbond fibersare generally not tacky when they are deposited onto a collectingsurface. Spunbond fibers may sometimes have diameters less than about 40microns, and are often between about 5 to about 20 microns.

As used herein, the terms “machine direction” or “MD” generally refersto the direction in which a material is produced. The term“cross-machine direction” or “CD” refers to the direction perpendicularto the machine direction. Dimensions measured in the cross-machinedirection are referred to as “width” dimension, while dimensionsmeasured in the machine direction are referred to as “length”dimensions.

As used herein, the term “elastomeric” and “elastic” and refers to amaterial that, upon application of a stretching force, is stretchable inat least one direction (such as the CD direction), and which uponrelease of the stretching force, contracts/returns to approximately itsoriginal dimension. For example, a stretched material may have astretched length that is at least 50% greater than its relaxedunstretched length, and which will recover to within at least 50% of itsstretched length upon release of the stretching force. A hypotheticalexample would be a one (1) inch sample of a material that is stretchableto at least 1.50 inches and which, upon release of the stretching force,will recover to a length of not more than 1.25 inches. Desirably, thematerial contracts or recovers at least 50%, and even more desirably, atleast 80% of the stretched length.

As used herein the terms “extensible” or “extensibility” generallyrefers to a material that stretches or extends in the direction of anapplied force by at least about 50% of its relaxed length or width. Anextensible material does not necessarily have recovery properties. Forexample, an elastomeric material is an extensible material havingrecovery properties. A meltblown web may be extensible, but not haverecovery properties, and thus, be an extensible, non-elastic material.

As used herein, the term “set” refers to retained elongation in amaterial sample following the elongation and recovery, i.e., after thematerial has been stretched and allowed to relax during a cycle test.

As used herein, the term “percent set” is the measure of the amount ofthe material stretched from its original length after being cycled (theimmediate deformation following the cycle test). The percent set iswhere the retraction curve of a cycle crosses the elongation axis. Theremaining strain after the removal of the applied stress is measured asthe percent set.

As used herein, the term “percent stretch” refers to the degree to whicha material stretches in a given direction when subjected to a certainforce. In particular, percent stretch is determined by measuring theincrease in length of the material in the stretched dimension, dividingthat value by the original dimension of the material, and thenmultiplying by 100. Such measurements are determined using the “stripelongation test”, which is substantially in accordance with thespecifications of ASTM D5035-95. Specifically, the test uses two clamps,each having two jaws with each jaw having a facing in contact with thesample. The clamps hold the material in the same plane, usuallyvertically, separated by 3 inches and move apart at a specified rate ofextension. The sample size is 3 inches by 6 inches, with a jaw facingheight of 1 inch and width of 3 inches, and a constant rate of extensionof 300 mm/min. The specimen is clamped in, for example, a Sintech 2/Stester with a Renew MTS mongoose box (control) and using TESTWORKS 4.07bsoftware (Sintech Corp, of Cary, N.C.). The test is conducted underambient conditions.

As used herein, the “hysteresis value” of a sample may be determined byfirst elongating the sample (“load up”) and then allowing the sample toretract (“load down”). The hysteresis value is the loss of energy duringthis cyclic loading.

DETAILED DESCRIPTION

Reference now will be made in detail to various embodiments of theinvention, one or more examples of which are set forth below. Eachexample is provided by way of explanation, not limitation of theinvention. In fact, it will be apparent to those skilled in the art thatvarious modifications and variations may be made in the presentinvention without departing from the scope or spirit of the invention.For instance, features illustrated or described as part of oneembodiment, may be used on another embodiment to yield a still furtherembodiment. Thus, it is intended that the present invention cover suchmodifications and variations.

Generally speaking, the present invention is directed to a nonwovencomposite that exhibits latent elastic properties. The composite isformed from an elastic strand layer laminated to a nonwoven web facing.Latent elasticity may be imparted to the elastic strand layer throughthe combination of a thermoplastic elastomer and a polyolefin capable offorming semi-crystalline domains among the elastomeric chains. Morespecifically, the elastic strand layer may be stretched in one or moredirections to orient the elastomer chains. Without intending to belimited by theory, the present inventors believe that the oriented stateof the chains may be held in place by the relatively stiffsemi-crystalline domains of the polyolefin. The stretched elastic strandlayer may subsequently be relaxed and bonded to a nonwoven web facing toform the composite. The composite may be later activated (e.g., heated)to shrink the elastic strand layer and provide it with “latent”stretchability. For instance, the composite may be heated at or abovethe softening temperature of the polyolefin to soften the crystallinedomains and allow the chains to return to their unoriented state. As aresult of the present invention, the elastic strand layer may beextended and recover from its unoriented state.

I. Elastic Strand Layer

The elastic strand layer of the present invention generally contains aplurality of elastic strands. The number of strands may vary as desired,such as from 5 to about 20, in some embodiments from about 7 to about18, and in some embodiments, from about 8 to 15 strands percross-directional inch. The strands may have a circular cross-section,but may alternatively have other cross-sectional geometries such aselliptical, rectangular as in ribbon-like strands, triangular,multi-lobal, etc. The diameter of the strands (the widestcross-sectional dimension) may vary as desired, such as within a rangeof from 0.1 to about 4 millimeters, in some embodiments from about 0.2to about 2.5 millimeters, and in some embodiments, from 0.5 to about 2millimeters. Further, the elastic strands may generally be arranged inany direction or pattern. For example, in one embodiment, the strandsare arranged in a direction that is substantially parallel to themachine direction and are desirably spaced apart from each other acrossthe cross machine direction at similar intervals.

If desired, the elastic strands may be substantially continuous inlength so that they are in the form of filaments. Such filaments may beproduced using any of a variety of known techniques, such as byextruding an elastomeric polymeric composition from a die having aseries of extrusion capillaries arranged in a row. As is well known inthe art, meltblown dies may be suitable for forming the filaments,except that the high velocity gas streams used in fiber attenuation aregenerally not employed. Rather, the molten polymer extrudate is pumpedfrom the die capillaries and allowed to extend away from the die underthe impetus of gravity. Besides extruded filaments, other elasticfilaments may also be employed in the present invention, such as thespandex-type materials available under the designation “LYCRA®” fromInvista North America of Wilmington, Del.

Regardless of the particular configuration of the strands, the elasticstrand layer of the present invention employs a combination of athermoplastic elastomer and a semi-crystalline polyolefin. Any of avariety of thermoplastic elastomers may generally be employed, such aselastomeric polyesters, elastomeric polyurethanes, elastomericpolyamides, elastomeric copolymers, and so forth, may be employed insome embodiments of the present invention. For example, thethermoplastic elastomer may be a substantially amorphous block copolymerhaving at least two blocks of a monoalkenyl arene polymer separated byat least one block of a saturated conjugated diene polymer. Themonoalkenyl arene blocks may include styrene and its analogues andhomologues, such as o-methyl styrene; p-methyl styrene; p-tert-butylstyrene; 1,3 dimethyl styrene p-methyl styrene; etc., as well as othermonoalkenyl polycyclic aromatic compounds, such as vinyl naphthalene;vinyl anthrycene; and so forth. Preferred monoalkenyl arenes are styreneand p-methyl styrene. The conjugated diene blocks may includehomopolymers of conjugated diene monomers, copolymers of two or moreconjugated dienes, and copolymers of one or more of the dienes withanother monomer in which the blocks are predominantly conjugated dieneunits. Preferably, the conjugated dienes contain from 4 to 8 carbonatoms, such as 1,3 butadiene (butadiene); 2-methyl-1,3 butadiene;isoprene; 2,3 dimethyl-1,3 butadiene; 1,3 pentadiene (piperylene); 1,3hexadiene; and so forth.

The amount of monoalkenyl arene (e.g., polystyrene) blocks may vary, buttypically constitute from about 8 wt. % to about 55 wt. %, in someembodiments from about 10 wt. % to about 35 wt. %, and in someembodiments, from about 25 wt. % to about 35 wt. % of the copolymer.Suitable block copolymers may contain monoalkenyl arene endblocks havinga number average molecular weight from about 5,000 to about 35,000 andsaturated conjugated diene midblocks having a number average molecularweight from about 20,000 to about 170,000. The total number averagemolecular weight of the block polymer may be from about 30,000 to about250,000.

Particularly suitable thermoplastic elastomers are available from KratonPolymers LLC of Houston, Tex. under the trade name KRATON®. KRATON®polymers include styrene-diene block copolymers, such asstyrene-butadiene, styrene-isoprene, styrene-butadiene-styrene, andstyrene-isoprene-styrene. KRATON® polymers also include styrene-olefinblock copolymers formed by selective hydrogenation of styrene-dieneblock copolymers. Examples of such styrene-olefin block copolymersinclude styrene-(ethylene-butylene), styrene-(ethylene-propylene),styrene-(ethylene-butylene)-styrene,styrene-(ethylene-propylene)-styrene,styrene-(ethylene-butylene)-styrene-(ethylene-butylene),styrene-(ethylene-propylene)-styrene-(ethylene-propylene), andstyrene-ethylene-(ethylene-propylene)-styrene. These block copolymersmay have a linear, radial or star-shaped molecular configuration.Specific KRATON® block copolymers include those sold under the brandnames G 1652, G 1657, G 1730, MD6673, and MD6937. Various suitablestyrenic block copolymers are described in U.S. Pat. Nos. 4,663,220,4,323,534, 4,834,738, 5,093,422 and 5,304,599, which are herebyincorporated in their entirety by reference thereto for all purposes.Other commercially available block copolymers include the S-EP-Selastomeric copolymers available from Kuraray Company, Ltd. of Okayama,Japan, under the trade designation SEPTON®. Still other suitablecopolymers include the S-I-S and S-B-S elastomeric copolymers availablefrom Dexco Polymers of Houston, Tex. under the trade designationVECTOR®. Also suitable are polymers composed of an A-B-A-B tetrablockcopolymer, such as discussed in U.S. Pat. No. 5,332,613 to Taylor, etal., which is incorporated herein in its entirety by reference theretofor all purposes. An example of such a tetrablock copolymer is astyrene-poly(ethylene-propylene)-styrene-poly(ethylene-propylene)(“S-EP-S-EP”) block copolymer.

Other exemplary thermoplastic elastomers that may be used includepolyurethane elastomeric materials such as, for example, those availableunder the trademark ESTANE from Noveon and LYCRA from Invista, polyamideelastomeric materials such as, for example, those available under thetrademark PEBAX (polyether amide) from Atofina Chemicals Inc., ofPhiladelphia, Pa., and polyester elastomeric materials such as, forexample, those available under the trade designation HYTREL from E.I.DuPont De Nemours & Company.

The semi-crystalline polyolefin of the elastic strand layer has or iscapable of exhibiting a substantially regular structure. That is,semi-crystalline polyolefins may be substantially amorphous in theirundeformed state, but form crystalline domains upon stretching. Thedegree of crystallinity of the olefin polymer may be from about 3% toabout 30%, in some embodiments from about 5% to about 25%, and in someembodiments, from about 5% and about 15%. Likewise, the semi-crystallinepolyolefin may have a latent heat of fusion (ΔH_(f)), which is anotherindicator of the degree of crystallinity, of from about 15 to about 75Joules per gram (“J/g”), in some embodiments from about 20 to about 65J/g, and in some embodiments, from 25 to about 50 J/g. Thesemi-crystalline polyolefin may also have a Vicat softening temperatureof from about 10° C. to about 100° C., in some embodiments from about20° C. to about 80° C., and in some embodiments, from about 30° C. toabout 60° C. The semi-crystalline polyolefin may have a meltingtemperature of from about 20° C. to about 120° C., in some embodimentsfrom about 35° C. to about 90° C., and in some embodiments, from about40° C. to about 80° C. The latent heat of fusion (ΔH_(f)) and meltingtemperature may be determined using differential scanning calorimetry(“DSC”) in accordance with ASTM D-3417 as is well known to those skilledin the art. The Vicat softening temperature may be determined inaccordance with ASTM D-1525.

Exemplary semi-crystalline polyolefins include polyethylene,polypropylene, blends and copolymers thereof. In one particularembodiment, a polyethylene is employed that is a copolymer of ethyleneand an α-olefin, such as a C₃-C₂₀ α-olefin or C₃-C₁₂ α-olefin. Suitableα-olefins may be linear or branched (e.g., one or more C₁-C₃ alkylbranches, or an aryl group). Specific examples include 1-butene;3-methyl-1-butene; 3,3-dimethyl-1-butene; 1-pentene; 1-pentene with oneor more methyl, ethyl or propyl substituents; 1-hexene with one or moremethyl, ethyl or propyl substituents; 1-heptene with one or more methyl,ethyl or propyl substituents; 1-octene with one or more methyl, ethyl orpropyl substituents; 1-nonene with one or more methyl, ethyl or propylsubstituents; ethyl, methyl or dimethyl-substituted 1-decene;1-dodecene; and styrene. Particularly desired α-olefin comonomers are1-butene, 1-hexene and 1-octene. The ethylene content of such copolymersmay be from about 60 mole % to about 99 mole %, in some embodiments fromabout 80 mole % to about 98.5 mole %, and in some embodiments, fromabout 87 mole % to about 97.5 mole %. The α-olefin content may likewiserange from about 1 mole % to about 40 mole %, in some embodiments fromabout 1.5 mole % to about 15 mole %, and in some embodiments, from about2.5 mole % to about 13 mole %.

The density of the polyethylene may vary depending on the type ofpolymer employed, but generally ranges from 0.85 to 0.96 grams per cubiccentimeter (“g/cm³”). Polyethylene “plastomers”, for instance, may havea density in the range of from 0.85 to 0.91 g/cm³. Likewise, “linear lowdensity polyethylene” (“LLDPE”) may have a density in the range of from0.91 to 0.940 g/cm³; “low density polyethylene” (“LDPE”) may have adensity in the range of from 0.910 to 0.940 g/cm³; and “high densitypolyethylene” (“HDPE”) may have density in the range of from 0.940 to0.960 g/cm³. Densities may be measured in accordance with ASTM 1505.

Particularly suitable polyethylene copolymers are those that are“linear” or “substantially linear.” The term “substantially linear”means that, in addition to the short chain branches attributable tocomonomer incorporation, the ethylene polymer also contains long chainbranches in the polymer backbone. “Long chain branching” refers to achain length of at least 6 carbons. Each long chain branch may have thesame comonomer distribution as the polymer backbone and be as long asthe polymer backbone to which it is attached. Preferred substantiallylinear polymers are substituted with from 0.01 long chain branch per1000 carbons to 1 long chain branch per 1000 carbons, and in someembodiments, from 0.05 long chain branch per 1000 carbons to 1 longchain branch per 1000 carbons. In contrast to the term “substantiallylinear”, the term “linear” means that the polymer lacks measurable ordemonstrable long chain branches. That is, the polymer is substitutedwith an average of less than 0.01 long chain branch per 1000 carbons.

The density of a linear ethylene/α-olefin copolymer is a function ofboth the length and amount of the α-olefin. That is, the greater thelength of the α-olefin and the greater the amount of α-olefin present,the lower the density of the copolymer. Although not necessarilyrequired, linear polyethylene “plastomers” are particularly desirable inthat the content of α-olefin short chain branching content is such thatthe ethylene copolymer exhibits both plastic and elastomericcharacteristics—i.e., a “plastomer.” Because polymerization withα-olefin comonomers decreases crystallinity and density, the resultingplastomer normally has a density lower than that of polyethylenethermoplastic polymers (e.g., LLDPE), but approaching and/or overlappingthat of an elastomer. For example, the density of the polyethyleneplastomer may be about 0.91 grams per cubic centimeter (g/cm³) or less,in some embodiments from about 0.85 to about 0.88 g/cm³, and in someembodiments, from about 0.85 g/cm³ to about 0.87 g/cm³. Despite having adensity similar to elastomers, plastomers generally exhibit a higherdegree of crystallinity, are relatively non-tacky, and may be formedinto pellets that are non-adhesive and relatively free flowing.

The distribution of the α-olefin comonomer within a polyethyleneplastomer is typically random and uniform among the differing molecularweight fractions forming the ethylene copolymer. This uniformity ofcomonomer distribution within the plastomer may be expressed as acomonomer distribution breadth index value (“CDBI”) of 60 or more, insome embodiments 80 or more, and in some embodiments, 90 or more.Further, the polyethylene plastomer may be characterized by a DSCmelting point curve that exhibits the occurrence of a single meltingpoint peak occurring in the region of 50 to 110° C. (second meltrundown).

Preferred plastomers for use in the present invention are ethylene-basedcopolymer plastomers available under the AFFINITY™ from Dow ChemicalCompany of Midland, Mich. Other suitable polyethylene plastomers areavailable under the designation ENGAGE™ from Dow Chemical Company ofMidland, Mich. and EXACT™ from ExxonMobil Chemical Company of Houston,Tex. Still other suitable ethylene polymers are available from The DowChemical Company under the designations DOWLEX™ (LLDPE) and ATTANE™(ULDPE). Other suitable ethylene polymers are described in U.S. Pat. No.4,937,299 to Ewen et al.; U.S. Pat. No. 5,218,071 to Tsutsui et al.;U.S. Pat. No. 5,272,236 to Lai et al.; and U.S. Pat. No. 5,278,272 toLai, et al., which are incorporated herein in their entirety byreference thereto for all purposes.

Of course, the present invention is by no means limited to the use ofethylene polymers. For instance, propylene polymers may also be suitablefor use as a semi-crystalline polyolefin. In one particular embodiment,the semi-crystalline propylene-based polymer includes a copolymer ofpropylene and an α-olefin, such as a C₂-C₂₀ α-olefin or C₂-C₁₂ α-olefin.Particularly desired α-olefin comonomers are ethylene, 1-butene,1-hexene and 1-octene. The propylene content of such copolymers may befrom about 60 mole % to about 99.5 wt. %, in some embodiments from about80 mole % to about 99 mole %, and in some embodiments, from about 85mole % to about 98 mole %. The α-olefin content may likewise range fromabout 0.5 mole % to about 40 mole %, in some embodiments from about 1mole % to about 20 mole %, and in some embodiments, from about 2 mole %to about 15 mole %. The distribution of the α-olefin comonomer istypically random and uniform among the differing molecular weightfractions forming the propylene copolymer. Although the density of thepropylene-based polymer employed in the present invention may vary, itis typically about 0.91 grams per cubic centimeter (g/cm³) or less, insome embodiments from about 0.85 to about 0.88 g/cm³, and in someembodiments, from about 0.85 g/cm³ to about 0.87 g/cm³. The melt flowrate of the propylene-based polymer may also be selected within acertain range to optimize the properties of the resulting elasticmaterial. The melt flow rate is the weight of a polymer (in grams) thatmay be forced through an extrusion rheometer orifice (0.0825-inchdiameter) when subjected to a force of 2160 grams in 10 minutes at 230°C. Generally speaking, the melt flow rate is high enough to improve meltprocessability, but not so high as to adversely interfere with bindingproperties. Thus, in most embodiments of the present invention, thepropylene-based polymer has a melt flow index of from about 0.1 to about10 grams per 10 minutes, in some embodiments from about 0.2 to about 5grams per 10 minutes, and in some embodiments, from about 0.5 to about 4grams per 10 minutes, measured in accordance with ASTM Test MethodD1238-E.

Suitable propylene polymers are commercially available under thedesignations VISTAMAXX™ from ExxonMobil Chemical Co. of Houston, Tex.;FINA™ (e.g., 8573) from Atofina Chemicals of Feluy, Belgium; TAFMER™available from Mitsui Petrochemical Industries; and VERSIFY™ availablefrom Dow Chemical Co. of Midland, Mich. Other examples of suitablepropylene polymers are described in U.S. Pat. No. 6,500,563 to Datta, etal.; U.S. Pat. No. 5,539,056 to Yang, et al.; and U.S. Pat. No.5,596,052 to Resconi, et al., which are incorporated herein in theirentirety by reference thereto for all purposes.

Any of a variety of known techniques may generally be employed to formthe semi-crystalline polyolefins. For instance, olefin polymers may beformed using a free radical or a coordination catalyst (e.g.,Ziegler-Natta). Preferably, the olefin polymer is formed from asingle-site coordination catalyst, such as a metallocene catalyst. Sucha catalyst system produces ethylene copolymers in which the comonomer israndomly distributed within a molecular chain and uniformly distributedacross the different molecular weight fractions. Metallocene-catalyzedpolyolefins are described, for instance, in U.S. Pat. No. 5,571,619 toMcAlpin et al.; U.S. Pat. No. 5,322,728 to Davis et al.; U.S. Pat. No.5,472,775 to Obijeski et al.; U.S. Pat. No. 5,272,236 to Lai et al.; andU.S. Pat. No. 6,090,325 to Wheat, et al., which are incorporated hereinin their entirety by reference thereto for all purposes. Examples ofmetallocene catalysts include bis(n-butylcyclopentadienyl)titaniumdichloride, bis(n-butylcyclopentadienyl)zirconium dichloride,bis(cyclopentadienyl )scandium chloride, bis(indenyl)zirconiumdichloride, bis(methylcyclopentadienyl)titanium dichloride,bis(methylcyclopentadienyl)zirconium dichloride, cobaltocene,cyclopentadienyltitanium trichloride, ferrocene, hafnocene dichloride,isopropyl(cyclopentadienyl,-1-flourenyl)zirconium dichloride,molybdocene dichloride, nickelocene, niobocene dichloride, ruthenocene,titanocene dichloride, zirconocene chloride hydride, zirconocenedichloride, and so forth. Polymers made using metallocene catalyststypically have a narrow molecular weight range. For instance,metallocene-catalyzed polymers may have polydispersity numbers(M_(w)/M_(n)) of below 4, controlled short chain branching distribution,and controlled isotacticity.

The melt flow index (MI) of the semi-crystalline polyolefins maygenerally vary, but is typically in the range of about 0.1 grams per 10minutes to about 100 grams per 10 minutes, in some embodiments fromabout 0.5 grams per 10 minutes to about 30 grams per 10 minutes, and insome embodiments, about 1 to about 10 grams per 10 minutes, determinedat 190° C. The melt flow index is the weight of the polymer (in grams)that may be forced through an extrusion rheometer orifice (0.0825-inchdiameter) when subjected to a force of 2.16 kilograms in 10 minutes at190° C., and may be determined in accordance with ASTM Test MethodD1238-E.

The relative amounts of the thermoplastic elastomers andsemi-crystalline polyolefins are selectively controlled in accordancewith the present invention to achieve a balance between the mechanicaland thermal properties of the elastic strand layer. For example, theratio of the amount of the thermoplastic elastomer(s) to the amount ofthe semi-crystalline polyolefin(s) may range from about 0.5 to about 15,in some embodiments from about 1 to about 10, and in some embodiments,from about 1 to about 5. The thermoplastic elastomer(s) may constitutefrom about 40 wt. % to about 95 wt. %, in some embodiments from about 45wt. % to about 90 wt. %, and in some embodiments, from about 50 wt. % toabout 75 wt. % of the elastic strand layer. Likewise, thesemi-crystalline polyolefin(s) may constitute from about 5 wt. % toabout 60 wt. %, in some embodiments from about 10 wt. % to about 55 wt.%, and in some embodiments, from about 15 wt. % to about 50 wt. % of theelastic strand layer. It should of course be understood that otherpolymers may also be employed in the elastic strand layer. Whenutilized, however, the other polymers typically constitute about 10 wt.% or less, and in some embodiments, about 5 wt. % or less of thematerial.

In addition to polymers, the elastic strand layer may also employ otheradditives as is known in the art. For example, although the elastomericpolymers may possess a certain amount of tack, a tackifying resin maynevertheless be employed in some embodiments to facilitate subsequentbonding of the strand layer to a nonwoven web facing. One suitable classof tackifying resins includes hydrogenated hydrocarbon resins, such asREGALREZ™ hydrocarbon resins available from Eastman Chemical. Othersuitable tackifying resins may be described in U.S. Pat. No. 4,787,699.When employed, the tackifying resin may be present in an amount fromabout 0.001 wt. % to about 35 wt. %, in some embodiments, from about0.005 wt. % to about 30 wt. %, and in some embodiments, from 0.01 wt. %to about 25 wt. % of the elastic strand layer.

The elastic strand layer may also contain other additives as is known inthe art, such as melt stabilizers, processing stabilizers, heatstabilizers, light stabilizers, antioxidants, heat aging stabilizers,whitening agents, antiblocking agents, bonding agents, viscositymodifiers, etc. Viscosity modifiers may also be employed, such aspolyethylene wax (e.g., EPOLENE™ C-10 from Eastman Chemical). Phosphitestabilizers (e.g., IRGAFOS available from Ciba Specialty Chemicals ofTerrytown, N.Y. and DOVERPHOS available from Dover Chemical Corp. ofDover, Ohio) are exemplary melt stabilizers. In addition, hindered aminestabilizers (e.g., CHIMASSORB available from Ciba Specialty Chemicals)are exemplary heat and light stabilizers. Further, hindered phenols arecommonly used as an antioxidant in the production of fibers and films.Some suitable hindered phenols include those available from CibaSpecialty Chemicals of under the trade name “Irganox®”, such as Irganox®1076, 1010, or E 201. Moreover, bonding agents may also be added tofacilitate bonding to additional materials (e.g., nonwoven web). Whenemployed, additives (e.g., antioxidant, stabilizer, etc.) may each bepresent in an amount from about 0.001 wt. % to about 40 wt. %, in someembodiments, from about 0.005 wt. % to about 35 wt. %, and in someembodiments, from 0.01 wt. % to about 25 wt. % of the elastic strandlayer.

The elastic strand layer may be in the form of a single layer of strandsor a laminate containing the strands. Depending on the particularconfiguration of the layer, the polymer content of the elastic strandsand/or other components of the layer may be selected to provide thedesired degree of latent elasticity to the composite. When used in asingle layer, for example, the elastic strands may be formed from ablend of a thermoplastic elastomer and semi-crystalline polyolefin. Inthis embodiment, the thermoplastic elastomer(s) may constitute fromabout 40 wt. % to about 95 wt. %, in some embodiments from about 45 wt.% to about 90 wt. %, and in some embodiments, from about 50 wt. % toabout 75 wt. % of the strands. Likewise, the semi-crystallinepolyolefin(s) may constitute from about 5 wt. % to about 60 wt. %, insome embodiments from about 10 wt. % to about 55 wt. %, and in someembodiments, from about 15 wt. % to about 50 wt. % of the strands.

In other embodiments of the present invention, the elastic strand layeris a laminate that includes multiple layers. For example, the laminatemay contain strands laminated to a meltblown web to help secure thestrands to a facing so that they are less likely to loosen during use.Examples of such laminates are described in more detail, for instance,in U.S. Pat. No. 5,385,775 to Wright and U.S. Patent ApplicationPublication No. 2005/0170729 to Stadelman. et al., which areincorporated herein in their entirety by reference thereto for allpurposes. The strands and the meltblown web m ay contain a thermoplasticelastomer, semi-crystalline polyolefin, or combinations thereof. In oneembodiment, the strands contain a thermoplastic elastomer and themeltblown web contains a semi-crystalline polyolefin. For example, thethermoplastic elastomer(s) may constitute about 70 wt. % or more, insome embodiments about 80 wt. % or more, and in some embodiments, about90 wt. % or more of the strands, while the semi-crystallinepolyolefin(s) may constitute about 70 wt. % or more, in some embodimentsabout 80 wt. % or more, and in some embodiments, about 90 wt. % or moreof the meltblown web. In this manner, the relatively stiffsemi-crystalline domains of the meltblown web may hold the elastomericchains of the strands in an oriented state (when stretched). Uponsubsequent heat activation, the semi-crystalline domains may be softenedand release oriented chains to impart latent elasticity to thecomposite.

Even when the meltblown web is formed from an elastomeric polymer, suchas described above, it is normally desired that the basis weight (oradd-on level) of the strands is greater than the meltblown web tooptimize the elasticity of the composite. However, too high of a strandbasis weight relative to the meltblown web basis weight may result in acomposite lacking the desired latency characteristics. Thus, the ratioof the strand basis weight to the meltblown web basis weight istypically from about 1.2 to about 5.0, in some embodiments from about1.5 to about 4.0, and in some embodiments, from about 2.0 to about 3.5.The basis weight of the meltblown layer (after stretching) may rangefrom about 0.1 to about 30 gram per square meter (“gsm”), in someembodiments about 0.5 to about 20 gsm, and in some embodiments, fromabout 1 to about 15 gsm. Likewise, the basis weight of the strands(after stretching) may range from about 1 to about 75 gsm, in someembodiments from about 4 to about 60 gsm, and in some embodiments, fromabout 5 to about 40 gsm.

Regardless of the particular manner in which it is formed, the elasticstrand layer of the present invention exhibits good latent stretchproperties for use in a wide variety of applications. One measurementthat is indicative of the latent stretch properties of the material isthe heat shrinkage performance, which is a measure of recoverabledeformation upon activation. A very high level of heat shrinkage may beachieved in the present invention, such as about 40% or more, in someembodiments about 50% or more, and in some embodiments, about 60% ormore. As described in the “Test Methods” below, heat shrinkage isdetermined by heating the material in water at 160° F. for 30 seconds to1 minute. Alternatively, shrinkage may be determined using ASTMD2838-02. Any known method of activation may generally be employed inthe present invention, including the application of heat, radiation(e.g., microwave), as well as chemical or mechanical treatments. Heatactivation may be accomplished at temperatures of from about 50° C. toabout 100° C., in some embodiments from about 60° C. to about 90° C.,and in some embodiments, from about 70° C. to about 80° C. Any of avariety of techniques may be used to apply heat to the elastic strandlayer, such as heated rolls, oven heating, and so forth.

II. Nonwoven Web Facing

A nonwoven web facing is generally employed in the present invention toreduce the coefficient of friction and enhance the cloth-like feel ofthe composite surface. Exemplary polymers for use in forming nonwovenweb facings may include, for instance, polyolefins, e.g., polyethylene,polypropylene, polybutylene, etc.; polytetrafluoroethylene; polyesters,e.g., polyethylene terephthalate and so forth; polyvinyl acetate;polyvinyl chloride acetate; polyvinyl butyral; acrylic resins, e.g.,polyacrylate, polymethylacrylate, polymethylmethacrylate, and so forth;polyamides, e.g., nylon; polyvinyl chloride; polyvinylidene chloride;polystyrene; polyvinyl alcohol; polyurethanes; polylactic acid;copolymers thereof; and so forth. If desired, biodegradable polymers,such as those described above, may also be employed. Synthetic ornatural cellulosic polymers may also be used, including but not limitedto, cellulosic esters; cellulosic ethers; cellulosic nitrates;cellulosic acetates; cellulosic acetate butyrates; ethyl cellulose;regenerated celluloses, such as viscose, rayon, and so forth. It shouldbe noted that the polymer(s) may also contain other additives, such asprocessing aids or treatment compositions to impart desired propertiesto the fibers, residual amounts of solvents, pigments or colorants, andso forth.

Monocomponent and/or multicomponent fibers may be used to form thenonwoven web facing. Monocomponent fibers are generally formed from apolymer or blend of polymers extruded from a single extruder.Multicomponent fibers are generally formed from two or more polymers(e.g., bicomponent fibers) extruded from separate extruders. Thepolymers may be arranged in substantially constantly positioned distinctzones across the cross-section of the fibers. The components may bearranged in any desired configuration, such as sheath-core,side-by-side, pie, island-in-the-sea, three island, bull's eye, orvarious other arrangements known in the art. Various methods for formingmulticomponent fibers are described in U.S. Pat. No. 4,789,592 toTaniguchi et al. and U.S. Pat. No. 5,336,552 to Strack et al., U.S. Pat.No. 5,108,820 to Kaneko, et al., U.S. Pat. No. 4,795,668 to Kruege, etal., U.S. Pat. No. 5,382,400 to Pike, et al., U.S. Pat. No. 5,336,552 toStrack, et al., and U.S. Pat. No. 6,200,669 to Marmon, et al., which areincorporated herein in their entirety by reference thereto for allpurposes. Multicomponent fibers having various irregular shapes may alsobe formed, such as described in U.S. Pat. No. 5,277,976 to Hogle, etal., U.S. Pat. No. 5,162,074 to Hills, U.S. Pat. No. 5,466,410 to Hills,U.S. Pat. No. 5,069,970 to Largman, et al., and U.S. Pat. No. 5,057,368to Largman, et al., which are incorporated herein in their entirety byreference thereto for all purposes.

Although any combination of polymers may be used, the polymers of themulticomponent fibers are typically made from thermoplastic materialswith different glass transition or melting temperatures where a firstcomponent (e.g., sheath) melts at a temperature lower than a secondcomponent (e.g., core). Softening or melting of the first polymercomponent of the multicomponent fiber allows the multicomponent fibersto form a tacky skeletal structure, which upon cooling, stabilizes thefibrous structure. For example, the multicomponent fibers may have fromabout 20% to about 80%, and in some embodiments, from about 40% to about60% by weight of the low melting polymer. Further, the multicomponentfibers may have from about 80% to about 20%, and in some embodiments,from about 60% to about 40%, by weight of the high melting polymer. Someexamples of known sheath-core bicomponent fibers available from KoSaInc. of Charlotte, N.C. under the designations T-255 and T-256, both ofwhich use a polyolefin sheath, or T-254, which has a low meltco-polyester sheath. Still other known bicomponent fibers that may beused include those available from the Chisso Corporation of Moriyama,Japan or Fibervisions LLC of Wilmington, Del.

Fibers of any desired length may be employed, such as staple fibers,continuous fibers, etc. In one particular embodiment, for example,staple fibers may be used that have a fiber length in the range of fromabout 1 to about 150 millimeters, in some embodiments from about 5 toabout 50 millimeters, in some embodiments from about 10 to about 40millimeters, and in some embodiments, from about 10 to about 25millimeters. Although not required, carding techniques may be employedto form fibrous layers with staple fibers as is well known in the art.For example, fibers may be formed into a carded web by placing bales ofthe fibers into a picker that separates the fibers. Next, the fibers aresent through a combing or carding unit that further breaks apart andaligns the fibers in the machine direction so as to form a machinedirection-oriented fibrous nonwoven web. The carded web may then bebonded using known techniques to form a bonded carded nonwoven web.

If desired, the nonwoven web facing used to form the nonwoven compositemay have a multi-layer structure. Suitable multi-layered materials mayinclude, for instance, spunbond/meltblown/spunbond (SMS) laminates andspunbond/meltblown (SM) laminates. Various examples of suitable SMSlaminates are described in U.S. Pat. No. 4,041,203 to Brock et al.; U.S.Pat. No. 5,213,881 to Timmons, et al.; U.S. Pat. No. 5,464,688 toTimmons, et al.; U.S. Pat. No. 4,374,888 to Bornslaeger; U.S. Pat. No.5,169,706 to Collier, et al.; and U.S. Pat. No. 4,766,029 to Brock etal., which are incorporated herein in their entirety by referencethereto for all purposes. In addition, commercially available SMSlaminates may be obtained from Kimberly-Clark Corporation under thedesignations Spunguard® and Evolution®.

Another example of a multi-layered structure is a spunbond web producedon a multiple spin bank machine in which a spin bank deposits fibersover a layer of fibers deposited from a previous spin bank. Such anindividual spunbond nonwoven web may also be thought of as amulti-layered structure. In this situation, the various layers ofdeposited fibers in the nonwoven web may be the same, or they may bedifferent in basis weight and/or in terms of the composition, type,size, level of crimp, and/or shape of the fibers produced. As anotherexample, a single nonwoven web may be provided as two or moreindividually produced layers of a spunbond web, a carded web, etc.,which have been bonded together to form the nonwoven web. Theseindividually produced layers may differ in terms of production method,basis weight, composition, and fibers as discussed above.

A nonwoven web facing may also contain an additional fibrous componentsuch that it is considered a composite. For example, a nonwoven web maybe entangled with another fibrous component using any of a variety ofentanglement techniques known in the art (e.g., hydraulic, air,mechanical, etc.). In one embodiment, the nonwoven web is integrallyentangled with cellulosic fibers using hydraulic entanglement. A typicalhydraulic entangling process utilizes high pressure jet streams of waterto entangle fibers to form a highly entangled consolidated fibrousstructure, e.g., a nonwoven web. Hydraulically entangled nonwoven websof staple length and continuous fibers are disclosed, for example, inU.S. Pat. No. 3,494,821 to Evans and U.S. Pat. No. 4,144,370 to Boulton,which are incorporated herein in their entirety by reference thereto forall purposes. Hydraulically entangled composite nonwoven webs of acontinuous fiber nonwoven web and a pulp layer are disclosed, forexample, in U.S. Pat. No. 5,284,703 to Everhart, et al. and U.S. Pat.No. 6,315,864 to Anderson, et al., which are incorporated herein intheir entirety by reference thereto for all purposes. The fibrouscomponent of the composite may contain any desired amount of theresulting substrate. The fibrous component may contain greater thanabout 50% by weight of the composite, and in some embodiments, fromabout 60% to about 90% by weight of the composite. Likewise, thenonwoven web may contain less than about 50% by weight of the composite,and in some embodiments, from about 10% to about 40% by weight of thecomposite.

Although not required, the nonwoven web facing may be necked in one ormore directions prior to lamination to the elastic strand layer of thepresent invention. Suitable necking techniques are described in U.S.Pat. Nos. 5,336,545, 5,226,992, 4,981,747 and 4,965,122 to Morman, aswell as U.S. Patent Application Publication No. 2004/0121687 to Morman,et al. Alternatively, the nonwoven web may remain relativelyinextensible in at least one direction prior to lamination to theelastic strand layer. In such embodiments, the nonwoven web may beoptionally stretched in one or more directions subsequent to laminationto the elastic strand layer.

The basis weight of the nonwoven web facing may generally vary, such asfrom about 5 grams per square meter (“gsm”) to 120 gsm, in someembodiments from about 8 gsm to about 70 gsm, and in some embodiments,from about 10 gsm to about 35 gsm. When multiple nonwoven web facings,such materials may have the same or different basis weights.

III. Lamination Technique

To achieve the desired latent elasticity of the composite, the elasticstrand layer is initially stretched in one or more directions to orientthe chains of the thermoplastic elastomer(s). Thereafter, the stretchedmaterial is relaxed to a certain degree and bonded to a nonwoven webfacing. Because the elastic strand layer is in a relaxed stated duringlamination, the nonwoven web facing does not gather to a significantextent. Thus, despite the fact that the composite contains anelastomeric polymer, its elastic properties are initially limited by thepresence of the relatively inelastic nonwoven web facing. Upon heatactivation, however, the semi-crystalline domains of the polyolefin maysoften and release the chains from their oriented configuration. Thiscauses the elastic strand layer to further shrink and thereby “gather”the nonwoven web facing. In this manner, the heat-activated composite isprovided with latent elasticity.

In this regard, various embodiments of the lamination method will now bedescribed in greater detail. Of course, it should be understood that thedescription provided below is merely exemplary, and that other methodsare contemplated by the present invention. Referring to FIG. 1, forinstance, one embodiment of a “horizontal” method for forming acontinuous filament laminate is shown. As shown, a first extrusionapparatus 20 is fed with the raw materials (e.g., thermoplasticelastomer) used to form the continuous filaments. The materials may bedry mixed together (i.e., without a solvent) or alternatively blendedwith a solvent. In the hopper, the materials are dispersively mixed inthe melt and compounded using any known technique, such as batch and/orcontinuous compounding techniques that employ, for example, a Banburymixer, Farrel continuous mixer, single screw extruder, twin screwextruder, etc. The first extrusion apparatus 20 extrudes the rawmaterials in the form of filaments 31 onto a forming surface 30 (e.g., aforaminous belt) moving clockwise about rolls 40. A vacuum (not shown)may also help hold the filaments 31 against the forming surface 30. Inthe illustrated embodiment, meltblown fibers 36 are also extruded froman extrusion apparatus 45 on top of the continuous filaments 31 to forma laminated elastic strand layer 50.

To impart the desired elasticity to the composite, the elastic strandlayer 50 is stretched in one or more directions. In FIG. 1, for example,the elastic strand layer 50 is stretched in the machine direction bypassing through a first set of rolls 46 traveling at a speed that isslower than a second set of rolls 47. While four rolls are illustratedin FIG. 1, it should be understood that the number of rolls may behigher or lower, depending on the level of stretch that is desired andthe degrees of stretching between each roll. To achieve the desiredlatent elasticity, various parameters of the stretching operation may beselectively controlled, including the stretch ratio, stretchingtemperature, and so forth. In some embodiments, for example, the elasticstrand layer is stretched in the machine direction at a ratio of fromabout 2.0 to about 8.0, in some embodiments from about 3.0 to about 7.0,and in some embodiments, from about 3.5 to about 6.0. The stretch ratiomay be determined by dividing the length of the stretched material byits length before stretching. The stretch ratio may also beapproximately the same as the draw ratio, which may be determined bydividing the linear speed of the strand layer upon stretching (e.g.,speed of the nip rolls) by the linear speed at which the strand layer isformed (e.g., speed of forming surface). In the illustrated embodiment,for example, the stretch ratio is determined by dividing the linearspeed of the second set of rolls 47 by the linear speed of the formingsurface 30.

The orientation temperature profile is also chosen to deliver thedesired shrink mechanical properties, such as shrink tension and shrinkpercentage. More specifically, the orientation temperature is less thanthe melting temperature of the semi-crystalline polyolefin. For example,the elastic strand layer may be stretched at a temperature from about15° C. to about 50° C., in some embodiments from about 25° C. to about40° C., and in some embodiments, from about 30° C. to about 40° C.Preferably, the elastic strand layer is “cold drawn”, i.e., stretchedwithout the application of external heat (e.g., heated rolls), toimprove latent elasticity.

A nonwoven web facing is also employed for laminating to the elasticstrand layer 50. For example, a nonwoven web facing 33 may simply beunwound from a supply roll 22 as shown in FIG. 1. Alternatively, thenonwoven web facing 33 may be formed in-line, such as by dispensingpolymer filaments from a pair of spinnerettes onto a conveyor assembly.The facing 33 may be compressed to form inter-filament bonding using apair of nip rolls (not shown). Following compaction, the nonwoven webfacing 33 is directed to a nip defined between rolls 58 for laminatingto the elastic strand layer 50. In FIG. 1, a second nonwoven web facing35 is also employed that originates from a supply roll 62.

As indicated above, the latent character of the elastic strand layer ofthe present invention may be enhanced by allowing it to relax prior tolamination to a nonwoven web facing. In some embodiments, for example,the elastic strand layer is allowed to relax about 10% or more, in someembodiments from about 15% to about 60%, and in some embodiments, fromabout 20% to about 50% in the machine direction. The aforementioned“relaxation percentage” may be determined by subtracting the relaxedlength of the strand layer by the stretched length of the layer,dividing this difference by the stretched length; and then multiplyingthe quotient by 100. If desired, the stretched and relaxed lengths ofthe layers may be determined from the speed of rolls used duringstretching and lamination. In the illustrated embodiment, for example,the relaxation percentage is determined by subtracting the linear speedof the nip rolls 58 from the linear speed of the rolls 47, dividing thisdifference by the linear speed of the rolls 47, and then multiplying thequotient by 100.

Various techniques may be utilized to bond the elastic strand layer 50to the nonwoven web facings 33 and 35, including adhesive bonding;thermal bonding; ultrasonic bonding; microwave bonding; extrusioncoating; and so forth. In one particular embodiment, one or both of therolls 58 apply a pressure to the strand layer 50 and facings 33 and 35to thermally bond the materials together. The rolls 58 may be smoothand/or contain a plurality of raised bonding elements. If desired, theelastic strand layer may itself act as an adhesive to facilitate bondingwith the nonwoven web facings 33 and 35. Other adhesives may also beemployed, such as Rextac 2730 and 2723 available from Huntsman Polymersof Houston, Tex., as well as adhesives available from Bostik Findley,Inc, of Wauwatosa, Wis. The type and basis weight of the adhesive usedwill be determined on the elastic attributes desired in the finalcomposite and end use. For instance, the basis weight of the adhesivemay be from about 1.0 to about 3.0 gsm. The adhesive may be applied tothe nonwoven web facings and/or the elastic strand layer prior tolamination using any known technique, such as slot or melt sprayadhesive systems.

The resulting composite 32 is wound and stored on a take-up roll 60.Optionally, the composite 32 may be allowed to slightly retract prior towinding on to the take-up roll 60. This may be achieved by using aslower linear velocity for the roll 60. More preferably, however, thecomposite 32 is kept under tension, such as by using the same linearvelocity for the roll 60 as the speed of one or more of the nip rolls58.

While not shown in FIG. 1, various additional potential processingand/or finishing steps known in the art, such as slitting, treating,printing graphics, etc., may be performed without departing from thespirit and scope of the invention. For instance, the composite mayoptionally be mechanically stretched in the cross-machine and/or machinedirections to enhance extensibility. In one embodiment, the compositemay be coursed through two or more rolls that have grooves in the CDand/or MD directions. Such grooved satellite/anvil roll arrangements aredescribed in U.S. Patent Application Publication Nos. 2004/0110442 toRhim, et al. and 2006/0151914 to Gerndt, et al., which are incorporatedherein in their entirety by reference thereto for all purposes. Forinstance, the laminate may be coursed through two or more rolls thathave grooves in the CD and/or MD directions. The grooved rolls may beconstructed of steel or other hard material (such as a hard rubber). Ifdesired, heat may be applied by any suitable method known in the art,such as heated air, infrared heaters, heated nipped rolls, or partialwrapping of the laminate around one or more heated rolls or steamcanisters, etc. Heat may also be applied to the grooved rollsthemselves. It should also be understood that other grooved rollarrangement are equally suitable, such as two grooved rolls positionedimmediately adjacent to one another. Besides grooved rolls, othertechniques may also be used to mechanically stretch the composite in oneor more directions. For example, the composite may be passed through atenter frame that stretches the composite. Such tenter frames are wellknown in the art and described, for instance, in U.S. Patent ApplicationPublication No. 2004/0121687 to Morman, et al. The composite may also benecked. Suitable techniques necking techniques are described in U.S.Pat. Nos. 5,336,545, 5,226,992, 4,981,747 and 4,965,122 to Morman, aswell as U.S. Patent Application Publication No. 2004/0121687 to Morman,et al., all of which are incorporated herein in their entirety byreference thereto for all purposes.

Although the embodiment shown in FIG. 1 depicts filaments formed in a“horizontal” extrusion process, it should be understood that othermethods are equally contemplated by the present invention. In analternative embodiment, for example, the filaments may be formed using a“vertical” extrusion process, such as described in U.S. PatentApplication Publication No. 2002/0104608 to Welch, et al., which isincorporated herein in its entirety by reference thereto for allpurposes. Referring to FIG. 2, for example, one embodiment of a methodfor forming a vertical filament laminate (“VFL”) is shown. As depicted,the method employs a vertically arranged apparatus that includes anextruder 110 for extruding continuous molten filaments 105 downward froma die onto a chilled positioning roll 120. As the filaments travel overthe surface of the roll 120, they are cooled and solidified. The chilledroll 120 may, for instance, have a temperature of about 40° F. to about80° F. The die of the extruder 110 may be positioned with respect to thechilled roll 120 so that the continuous filaments meet the roll at apredetermined angle 130. An angled, or canted, orientation provides anopportunity for the filaments to emerge from the die at a right angle tothe roll tangent point resulting in improved spinning, more efficientenergy transfer, and generally longer die life. The angle 130 betweenthe die exit of the extruder 110 and the vertical axis (or thehorizontal axis of the first roll, depending on which angle is measured)may be as little as a few degrees or as much as 90°. The optimum anglemay vary as a function of extrudate exit velocity, roll speed, verticaldistance from the die to the roll, and horizontal distance from the diecenterline to the top dead center of the roll.

After the filaments 105 are quenched and solidified, they are stretchedor elongated using a series of stretch rolls 140. The series of stretchrolls 140 may include one or more individual stretch rolls, and suitablyat least two stretch rolls 145 and 160 as shown in FIG. 2. The stretchrolls 145 and 160 rotate at a speed greater than a speed at which thechill roll 120 rotates, thereby stretching the filaments 105. In oneembodiment of this invention, each successive roll rotates at a speedgreater than the speed of the previous roll. Upon stretching, thefilaments 105 are then allowed to relax prior to entering a nip formedbetween rolls 165. Nonwoven web facings 155 and 185 are unwound fromsupply rolls 154 and 184, respectively, and also supplied to the nip forlamination to the filaments 105. The resulting composite 132 is woundand stored on a take-up roll 160 as described above.

Generally speaking, composites may be formed according to the presentinvention that are relatively inelastic prior to heat activation. Oneparameter that is indicative of the dimensional stability of thecomposite prior to heat activation is the percent strain that itundergoes at a load of 2000 grams-force per 3 inches wide (sample width)according to the “stretch to stop” test, which is described in moredetail below. More specifically, the composite typically has a percentstrain of about 50% or less in the machine direction, in someembodiments about 40% or less in the machine direction, and in someembodiments, about 25% or less in the machine direction prior to heatactivation. After heat shrinkage, the composite typically has a percentstrain of about 50% or more in the machine direction, in someembodiments about 75% or more in the machine direction, and in someembodiments, from about 100% to about 200% in the machine direction.Furthermore, the potential shrinkage of the composite may be about 40%or more, in some embodiments about 50% or more, and in some embodiments,about 60% or more.

As a result of the present invention, the composite may be more easilyprocessed into an end product because it is less elastic prior toactivation, and thus more dimensionally stable. This allows thecomposite to be more readily processed, e.g., printed, rolled orunrolled, converted into a final product, etc. In one embodiment, forexample, a latent elastic composite may be incorporated into anabsorbent article. During the conversion process, the latent elasticcomposite may be activated through the application of heat, such asduring the curing process for an adhesive used to attach togethervarious components of the product. Because the latent elastic compositehas a greater dimensional stability prior to activation than highlyelastic materials, enhanced processing efficiencies may be realized. Forexample, the composite need not be maintained in a mechanicallystretched condition during attachment to other components of theproduct. This allows for greater freedom in the location and manner inwhich the adhesive is applied.

The latent elastic composite of the present invention may be used in awide variety of applications. As noted above, for example, the elasticcomposite may be used in an absorbent article. An “absorbent article”generally refers to any article capable of absorbing water or otherfluids. Examples of some absorbent articles include, but are not limitedto, personal care absorbent articles, such as diapers, training pants,absorbent underpants, incontinence articles, feminine hygiene products(e.g., sanitary napkins), swim wear, baby wipes, and so forth; medicalabsorbent articles, such as garments, fenestration materials, underpads,bedpads, bandages, absorbent drapes, and medical wipes; food servicewipers; clothing articles; and so forth. Materials and processessuitable for forming such absorbent articles are well known to thoseskilled in the art. Typically, absorbent articles include asubstantially liquid-impermeable layer (e.g., outer cover), aliquid-permeable layer (e.g., bodyside liner, surge layer, etc.), and anabsorbent core. In one particular embodiment, the elastic strand layerof the present invention may be used in providing elastic waist, legcuff/gasketing, stretchable ear, side panel or stretchable outer coverapplications.

Various embodiments of an absorbent article that may be formed accordingto the present invention will now be described in more detail. Referringto FIG. 3, for example, one embodiment of a disposable diaper 250 isshown that generally defines a front waist section 255, a rear waistsection 260, and an intermediate section 265 that interconnects thefront and rear waist sections. The front and rear waist sections 255 and260 include the general portions of the diaper which are constructed toextend substantially over the wearer's front and rear abdominal regions,respectively, during use. The intermediate section 265 of the diaperincludes the general portion of the diaper that is constructed to extendthrough the wearer's crotch region between the legs. Thus, theintermediate section 265 is an area where repeated liquid surgestypically occur in the diaper.

The diaper 250 includes, without limitation, an outer cover, orbacksheet 270, a liquid permeable bodyside liner, or topsheet, 275positioned in facing relation with the backsheet 270, and an absorbentcore body, or liquid retention structure, 280, such as an absorbent pad,which is located between the backsheet 270 and the topsheet 275. Thebacksheet 270 defines a length, or longitudinal direction 286, and awidth, or lateral direction 285 which, in the illustrated embodiment,coincide with the length and width of the diaper 250. The liquidretention structure 280 generally has a length and width that are lessthan the length and width of the backsheet 270, respectively. Thus,marginal portions of the diaper 250, such as marginal sections of thebacksheet 270 may extend past the terminal edges of the liquid retentionstructure 280. In the illustrated embodiments, for example, thebacksheet 270 extends outwardly beyond the terminal marginal edges ofthe liquid retention structure 280 to form side margins and end marginsof the diaper 250. The topsheet 275 is generally coextensive with thebacksheet 270 but may optionally cover an area that is larger or smallerthan the area of the backsheet 270, as desired.

To provide improved fit and to help reduce leakage of body exudates fromthe diaper 250, the diaper side margins and end margins may beelasticized with suitable elastic members, as further explained below.For example, as representatively illustrated in FIG. 3, the diaper 250may include leg elastics 290 constructed to operably tension the sidemargins of the diaper 250 to provide elasticized leg bands which canclosely fit around the legs of the wearer to reduce leakage and provideimproved comfort and appearance. Waist elastics 295 are employed toelasticize the end margins of the diaper 250 to provide elasticizedwaistbands. The waist elastics 295 are configured to provide aresilient, comfortably close fit around the waist of the wearer. Thelatently elastic materials of the present invention are suitable for useas the leg elastics 290 and waist elastics 295. Exemplary of suchmaterials are laminate sheets that either comprise or are adhered to thebacksheet, such that elastic constrictive forces are imparted to thebacksheet 270.

As is known, fastening means, such as hook and loop fasteners, may beemployed to secure the diaper 250 on a wearer. Alternatively, otherfastening means, such as buttons, pins, snaps, adhesive tape fasteners,cohesives, fabric-and-loop fasteners, or the like, may be employed. Inthe illustrated embodiment, the diaper 250 includes a pair of sidepanels 300 (or ears) to which the fasteners 302, indicated as the hookportion of a hook and loop fastener, are attached. Generally, the sidepanels 300 are attached to the side edges of the diaper in one of thewaist sections 255, 260 and extend laterally outward therefrom. The sidepanels 300 may be elasticized or otherwise rendered elastomeric by useof a latently elastic materials of the present invention. Examples ofabsorbent articles that include elasticized side panels and selectivelyconfigured fastener tabs are described in PCT Patent Application WO95/16425 to Roessler; U.S. Pat. No. 5,399,219 to Roessler et al.; U.S.Pat. No. 5,540,796 to Fries; and U.S. Pat. No. 5,595,618 to Fries, eachof which is incorporated herein in its entirety by reference thereto forall purposes.

The diaper 250 may also include a surge management layer 305, locatedbetween the topsheet 275 and the liquid retention structure 280, torapidly accept fluid exudates and distribute the fluid exudates to theliquid retention structure 280 within the diaper 250. The diaper 250 mayfurther include a ventilation layer (not illustrated), also called aspacer, or spacer layer, located between the liquid retention structure280 and the backsheet 270 to insulate the backsheet 270 from the liquidretention structure 280 to reduce the dampness of the garment at theexterior surface of a breathable outer cover, or backsheet, 270.Examples of suitable surge management layers 305 are described in U.S.Pat. No. 5,486,166 to Bishop and U.S. Pat. No. 5,490,846 to Ellis.

As representatively illustrated in FIG. 3, the disposable diaper 250 mayalso include a pair of containment flaps 310 which are configured toprovide a barrier to the lateral flow of body exudates. The containmentflaps 310 may be located along the laterally opposed side edges of thediaper adjacent the side edges of the liquid retention structure 280.Each containment flap 310 typically defines an unattached edge that isconfigured to maintain an upright, perpendicular configuration in atleast the intermediate section 265 of the diaper 250 to form a sealagainst the wearer's body. The containment flaps 310 may extendlongitudinally along the entire length of the liquid retention structure280 or may only extend partially along the length of the liquidretention structure. When the containment flaps 310 are shorter inlength than the liquid retention structure 280, the containment flaps310 can be selectively positioned anywhere along the side edges of thediaper 250 in the intermediate section 265. Such containment flaps 310are generally well known to those skilled in the art. For example,suitable constructions and arrangements for containment flaps 310 aredescribed in U.S. Pat. No. 4,704,116 to Enloe.

The diaper 250 may be of various suitable shapes. For example, thediaper may have an overall rectangular shape, T-shape or anapproximately hour-glass shape. In the shown embodiment, the diaper 250has a generally I-shape. Other suitable components which may beincorporated on absorbent articles of the present invention may includewaist flaps and the like which are generally known to those skilled inthe art. Examples of diaper configurations suitable for use inconnection with the latently elastic materials of the present inventionthat may include other components suitable for use on diapers aredescribed in U.S. Pat. No. 4,798,603 to Meyer et al.; U.S. Pat. No.5,176,668 to Bernardin; U.S. Pat. No. 5,176,672 to Bruemmer et al.; U.S.Pat. No. 5,192,606 to Proxmire et al.; and U.S. Pat. No. 5,509,915 toHanson et al., which are incorporated herein in their entirety byreference thereto for all purposes.

The various regions and/or components of the diaper 201 may be assembledtogether using any known attachment mechanism, such as adhesive,ultrasonic, thermal bonds, etc. Suitable adhesives may include, forinstance, hot melt adhesives, pressure-sensitive adhesives, and soforth. When utilized, the adhesive may be applied as a uniform layer, apatterned layer, a sprayed pattern, or any of separate lines, swirls ordots. In the illustrated embodiment, for example, the topsheet 275 andbacksheet 270 may be assembled to each other and to the liquid retentionstructure 280 with lines of adhesive, such as a hot melt,pressure-sensitive adhesive. Similarly, other diaper components, such asthe elastic members 290 and 295, fastening members 302, and surge layer305 may be assembled into the article by employing the above-identifiedattachment mechanisms.

Although various configurations of a diaper have been described above,it should be understood that other diaper and absorbent articleconfigurations are also included within the scope of the presentinvention. In addition, the present invention is by no means limited todiapers. In fact, several examples of absorbent articles are describedin U.S. Pat. No. 5,649,916 to DiPalma, et al.; U.S. Pat. No. 6,110,158to Kielpikowski; U.S. Pat. No. 6,663,611 to Blaney, et al., which areincorporated herein in their entirety by reference thereto for allpurposes. Further, other examples of personal care products that mayincorporate such materials are training pants (such as in side panelmaterials) and feminine care products. By way of illustration only,training pants suitable for use with the present invention and variousmaterials and methods for constructing the training pants are disclosedin U.S. Pat. No. 6,761,711 to Fletcher et al.; U.S. Pat. No. 4,940,464to Van Gompel et al.; U.S. Pat. No. 5,766,389 to Brandon et al.; andU.S. Pat. No. 6,645,190 to Olson et al., which are incorporated hereinin their entirety by reference thereto for all purposes.

The present invention may be better understood with reference to thefollowing examples.

Test Methods

% Heat Shrinkage

To measure heat-activated retraction, marks spaced 100 millimeters apartare placed on the material while it is still under tension on the roll.The material is then released from tension on the roll and a length ofmaterial containing the marks is cut from the roll. Immediately afterreleasing the material and cutting it, the distance between the marks ismeasured again to determine the initial length (Before Heated RetractionLength or “BHRL”). The material is then submerged in water (160° F.) forat least 30 seconds, but no more than 1 minute. Thereafter, the distancebetween the marks is again measured (After Heated Retraction Length or“AHRL”). The percent shrinkage is indicative of the latent elasticity ofthe material and is calculated by the following equation:

% shrinkage=100*(BHRL−AHRL)/BHRL

Three measurements are averaged for each sample to be tested. Themeasurements are taken at ambient conditions.

Cycle Testing

The materials were tested using a cyclical testing procedure todetermine load loss and percent set. In particular, 2-cycle testing wasutilized to 100% defined elongation. For this test, the sample size was3 inches (7.6 centimeters) in the cross-machine direction by 6 inches inthe machine direction. The Grip size was 3 inches (7.6 centimeters) inwidth. The grip separation was 4 inches. The samples were loaded suchthat the machine direction of the sample was in the vertical direction.A preload of approximately 20 to 30 grams was set. The test pulled thesample to 100% elongation at a speed of 20 inches (50.8 centimeters) perminute, and then immediately (without pause) returned to the zero at aspeed of 20 inches (50.8 centimeters) per minute. The results of thetest data are all from the first and second cycles. The testing was doneon a Sintech Corp. constant rate of extension tester 2/S with a RenewMTS mongoose box (control) using TESTWORKS 4.07b software (Sintech Corp,of Cary, N.C.). The tests were conducted under ambient conditions.

Stretch-to-Stop

The materials were tested to determine the ability of the material toundergo elongation upon application of a tensioning. More specifically,the percent strain of the material at a load of 2000 grams-force wasdetermined by subtracting the maximum extended dimension of the materialfrom its unextended dimension, dividing that difference by theunextended dimension, and then multiplying by 100. Such measurements aredetermined using the “strip elongation test”, which is substantially inaccordance with the specifications of ASTM D5035-95. The test uses twoclamps, each having two jaws with each jaw having a facing in contactwith the sample. The clamps hold the material in the same plane and moveapart at a specified rate of extension. A sample size of 3 inches (7.6centimeters) in the cross-machine direction by 7 inches (17.8centimeters) in the machine direction was selected. The grip size was 3inches (7.6 centimeters) in width, and intermeshing grips were utilizedso that material would not slip while tested. The grip separation was100 millimeters. The samples were loaded so that the machine directionof the sample was in the vertical direction. A preload of approximately20 to 30 grams-force was set. The test pulled the sample until 2000grams-force of tension was produced, and then the test stopped. The testspeed was 500 millimeters per minute of extension or strain. The testreported the elongation or strain in percent from start when 2000grams-force of tension was produced (per 3 inches in width of thematerial). The testing was done on a Sintech Corp. constant rate ofextension tester 2/S with a Renew MTS mongoose box (controller) usingTESTWORKS 4.07b software (Sintech Corp, of Cary, N.C.). The tests wereconducted under ambient conditions. Results are generally reported as anaverage of three specimens and may be performed with the specimen in thecross direction (CD) and/or the machine direction (MD).

EXAMPLE 1

Six samples (Nos. 1-6) of a continuous filament/meltblown laminate wereinitially formed using the “horizontal” method shown in FIG. 1. Thefilaments were formed from 100 wt. % KRATON® MD6673 (Kraton Polymers,LLC of Houston Tex.). KRATON® MD6673 contains 68 wt. % of astyrene-ethylene-butylene-styrene block copolymer (KRATON® MD6937), 20wt. % REGALREZ™ 1126 (Eastman Chemical) and 12 wt. % EPOLENE™ C-10polyethylene wax (Eastman Chemical). The meltblown web was formed from80 wt. % of AFFINITY EG8185 (Dow Chemical Co.) and 20 wt. % REGALREZ™1126 (Eastman Chemical). AFFINITY EG8185 is a metallocene-catalyzedpolyethylene plastomer having a density of 0.885 grams per cubiccentimeter, a peak melting temperature of 83° C., and a melt index of 30grams per 10 minutes (190° C., 2.16 kg).

A 1.5″ Killion extruder was used to extrude the parallel continuousfilaments and a 3″ Beloit extruder was used to produce the meltblownfibers. The extruder temperatures were set at 500° F. and 420° F. forthe 1.5″ and 3″ extruders, respectively. The filament die had 12 holesper inch, each hole having a diameter of 0.9 millimeters. The filamentswere first laid down on a foraminous wire and then the meltblown fiberswere formed on top of the filaments. The filament/meltblown structurewas removed from the forming wire at a speed of 20 feet per minute andthen passed through S-wrap rollers operating at a speed of 100 feet perminute, thereby stretching the structure at a stretch ratio of about 5.0in the machine direction. The samples were then passed through twosmooth calender rolls and thermally bonded to a polypropylene spunbondfacing having a basis weight of approximately 13.6 grams per squaremeter. For Sample Nos. 1-3, the calender rolls operated at a speed of 70feet per minute so that the filament/meltblown structure was allowed torelax about 30% before lamination to the spunbond facing. For SampleNos. 4-6, the calender rolls operated at a speed of 60 feet per minuteso that the filament/meltblown structure was allowed to relax about 40%before lamination to the spunbond facing. The resulting laminates werethen wound onto a roll operating at the same speed as the smooth rollcalender rolls.

The specific processing conditions and web properties are set forth inmore detail below in Tables 1-2.

TABLE 1 Process Conditions Filament Meltblown Extruder Extruder WireS-Wrap #1 S-wrap #2 Calender Winder Speed Speed Speed Speed StretchSpeed Speed Speed Sample (RPM) (RPM) (ft/min) (ft/min) Ratio (ft/min)Relaxation % (ft/min) (ft/min) 1 8.6 9.0 20 20 5 100 30 70 70 2 6.9 9.020 20 5 100 30 70 70 3 5.2 9.0 20 20 5 100 30 70 70 4 5.2 9.0 20 20 5100 40 60 60 5 6.9 9.0 20 20 5 100 40 60 60 6 8.6 9.0 20 20 5 100 40 6060

TABLE 2 Web Properties Filament Meltblown Basis Wt. Basis Wt. AfterAfter Stretching Stretching Ratio of Filament Basis Wt. to Sample (gsm)(gsm) Meltblown Basis Wt. 1 25 10 2.45 2 20 10 2.03 3 15 10 1.50 4 15 101.50 5 20 10 3.03 6 25 10 2.45

EXAMPLE 2

Three (3) samples (Sample Nos. 7-9) of a continuous filament/meltblownlaminate were initially formed using the “horizontal” method shown inFIG. 1. The filaments were formed from 100 wt. % KRATON® MD6673 (KratonPolymers, LLC of Houston Tex.). The meltblown web was formed from 80 wt.% of AFFINITY EG8185 (Dow Chemical Co.) and 20 wt. % REGALREZ™ 1126(Eastman Chemical). A 1.5″ Killion extruder was used to extrude theparallel continuous filaments and a 3″ Beloit extruder was used toproduce the meltblown fibers. The extruder temperatures were set at 500°F. and 420° F. for the 1.5″ and 3″ extruders, respectively. The filamentdie had 12 holes per inch, each hole having a diameter of 0.9millimeters. The filaments were first laid down on a foraminous wire andthen the meltblown fibers were formed on top of the filaments. Thefilament/meltblown structure was removed from the forming wire at aspeed of 20 feet per minute and then passed through S-wrap rollersoperating at a speed of 100 feet per minute, thereby stretching thestructure at a stretch ratio of about 5.0 in the machine direction. Thesamples were then passed through two smooth calender rolls and thermallybonded to a polypropylene spunbond facing having a basis weight ofapproximately 13.6 grams per square meter. The calender rolls operatedat a speed of 100 feet per minute so that the filament/meltblownstructure remained under tension during lamination. The resultinglaminates were then wound onto a roll operating at a speed of 70 feetper minute.

The specific processing conditions and web properties are set forth inmore detail below in Tables 3-4.

TABLE 3 Process Conditions Filament Meltblown Extruder Extruder WireS-Wrap #1 Calender Winder Speed Speed Speed Speed Speed Speed Sample(RPM) (RPM) (ft/min) (ft/min) Strech Ratio (ft/min) (ft/min) 7 8.6 9.020 20 5 100 70 8 6.9 9.0 20 20 5 100 70 9 5.2 9.0 20 20 5 100 70

TABLE 4 Web Properties Filament Meltblown Basis Wt. After Basis Wt.After Stretching Streching Ratio of Filament Basis Wt. to Sample (gsm)(gsm) Meltblown Basis Wt. 7 25 10 2.45 8 20 10 2.03 9 15 10 1.50

EXAMPLE 3

The materials of Examples 1 and 2 were heat activated and cycle testedas described above. The results are set forth below in Table 5.

TABLE 5 Composite Properties Cycle 1 Cycle 2 Load Load Load Load LoadLoad BHRL AHRL up up down up up down Sample (mm) (mm) % Shrinkage 50%100% 50% Hyst. % 50% 100% 50% Set % 1 87 45 48 917 1239 608 30.1 7511201 591 9.0 2 83 39 53 770 1065 508 29.9 629 1031 494 9.4 3 90 36 60569 841 343 33.6 452 813 333 12.1 4 95 42 56 583 913 337 35.9 454 877325 12.1 5 91 43 53 743 1060 462 33.4 591 1028 448 10.3 6 90 46 49 9001253 583 31.5 729 1213 568 9.4 7 91 52 43 879 1182 589 29.5 727 1150 5749.0 8 87 45 48 728 992 475 30.8 599 965 462 10.1 9 84 41 52 633 880 38435.1 506 856 374 10.9

As indicated, the samples provided good elastic behavior after heatactivation as exhibited by their hysteresis and set as obtained throughcycle testing. Additionally, the samples exhibited good latency behaviorthrough their BHRL and AHRL results. Additional portions of Sample Nos.2 and 8 were further heat activated and “stretch to stop” tested asdescribed above. The results are set forth below in Table 6.

TABLE 6 Composite Properties BHRL AHRL % Stretch to Stop % Stretch toStop Sample (mm) (mm) % Shrinkage (Before Heat Shrinkage) (After HeatShrinkage) 2 93 44 53 22 159 8 90 45 50 71 241

As indicated, Sample No. 2 had a low stretch-to-stop value prior to heatactivation and high value after heat activation, which is indicative ofa material that is relatively inelastic prior to heat activation, butelastic after heat activation.

While the invention has been described in detail with respect to thespecific embodiments thereof, it will be appreciated that those skilledin the art, upon attaining an understanding of the foregoing, mayreadily conceive of alterations to, variations of, and equivalents tothese embodiments. Accordingly, the scope of the present inventionshould be assessed as that of the appended claims and any equivalentsthereto.

1. A method of forming a nonwoven composite having latent elasticity,the method comprising: forming an elastic strand layer comprising aplurality of elastic strands, wherein the elastic strand layer is formedfrom a thermoplastic elastomer and semi-crystalline polyolefin;stretching the elastic strand layer in the machine direction at astretch ratio from about 2.0 to about 8.0, thereby forming a stretchedelastic strand layer; allowing the stretched elastic strand layer torelax to achieve a relaxation percentage of about 10% or more; andlaminating a nonwoven web facing to the relaxed elastic strand layer. 2.The method of claim 1, wherein the elastic strand layer is stretched ata stretch ratio of from about 3.5 to about 6.0.
 3. The method of claim1, wherein the relaxation percentage is about 20% to about 50%.
 4. Themethod of claim 1, wherein the elastic strand layer is also stretched inthe cross-machine direction.
 5. The method of claim 1, furthercomprising winding the composite onto a roll, wherein the composite issubstantially inhibited from retracting in the machine direction duringwinding onto the roll.
 6. The method of claim 1, wherein thethermoplastic elastomer is selected from the group consisting ofstyrene-butadiene, styrene-isoprene, styrene-butadiene-styrene,styrene-isoprene-styrene, styrene-(ethylene-butylene),styrene-(ethylene-propylene), styrene-(ethylene-butylene)-styrene,styrene-(ethylene-propylene)-styrene,styrene-(ethylene-butylene)-styrene-(ethylene-butylene),styrene-(ethylene-propylene)-styrene-(ethylene-propylene), andstyrene-ethylene-(ethylene-propylene)-styrene, and combinations thereof.7. The method of claim 1, wherein the semi-crystalline polyolefin has adensity of about 0.91 grams per cubic centimeter or less.
 8. The methodof claim 1, wherein the semi-crystalline polyolefin is anethylene/α-olefin copolymer, propylene/α-olefin copolymer, or acombination thereof.
 9. The method of claim 1, wherein thesemi-crystalline polyolefin is single-site catalyzed.
 10. The method ofclaim 1, wherein thermoplastic elastomers constitute from about 40 wt. %to about 95 wt. % of the elastic strand layer and semi-crystallinepolyolefins constitute from about 5 wt. % to about 60 wt. % of theelastic strand layer.
 11. The method of claim 1, wherein thermoplasticelastomers constitute from about 45 wt. % to about 90 wt. % of theelastic strand layer and semi-crystalline polyolefins constitute fromabout 15 wt. % to about 55 wt. % of the elastic strand layer.
 12. Themethod of claim 1, wherein the strands are in the form of an array ofcontinuous filaments.
 13. The method of claim 12, wherein the filamentsare formed from a blend of the thermoplastic elastomer andsemi-crystalline polyolefin.
 14. The method of claim 12, wherein theelastic strand layer further comprises a meltblown web laminated to thefilaments.
 15. The method of claim 14, wherein the meltblown webcontains the semi-crystalline polyolefin and the filaments contain thethermoplastic elastomer.
 16. The method of claim 14, wherein the ratioof the basis weight of the filaments to the basis weight of themeltblown web is from about 1.2 to about 5.0.
 17. The method of claim 1,wherein the nonwoven web facing contains a spunbond web, meltblown web,or a combination thereof.
 18. The nonwoven composite of claim 1, furthercomprising laminating a second nonwoven web facing to the relaxedelastic strand layer.
 19. A nonwoven composite having latent elasticity,the composite comprising an elastic strand layer laminated to a nonwovenweb facing, the elastic strand layer comprising a plurality of elasticstrands and being formed from at least one thermoplastic elastomer andat least one semi-crystalline polyolefin, wherein the semi-crystallinepolyolefin constitutes from about 5 wt. % to about 60 wt. % of theelastic strand layer and the thermoplastic elastomer constitutes fromabout 40 wt. % to about 95 wt. % of the elastic strand layer, whereinthe composite exhibits a percent strain of about 50% or less whensubjected to a load of 2000 grams-force per 3 inches wide in the machinedirection prior to heat activation.
 20. The nonwoven composite of claim19, wherein the thermoplastic elastomer is selected from the groupconsisting of styrene-butadiene, styrene-isoprene,styrene-butadiene-styrene, styrene-isoprene-styrene,styrene-(ethylene-butylene), styrene-(ethylene-propylene),styrene-(ethylene-butylene)-styrene,styrene-(ethylene-propylene)-styrene,styrene-(ethylene-butylene)-styrene-(ethylene-butylene),styrene-(ethylene-propylene)-styrene-(ethylene-propylene), andstyrene-ethylene-(ethylene-propylene)-styrene, and combinations thereof.21. The nonwoven composite of claim 19, wherein the semi-crystallinepolyolefin has a density of about 0.91 grams per cubic centimeter orless and is single-site catalyzed.
 22. The nonwoven composite of claim19, wherein the semi-crystalline polyolefin is an ethylene/α-olefincopolymer, a propylene/α-olefin copolymer, or a combination thereof. 23.The nonwoven composite of claim 19, wherein the thermoplastic elastomerconstitutes from about 45 wt. % to about 90 wt. % of the elastic strandlayer and the semi-crystalline polyolefin constitutes from about 10 wt.% to about 55 wt. % of the elastic strand layer.
 24. The nonwovencomposite of claim 19, wherein the strands are in the form of an arrayof continuous filaments.
 25. The nonwoven composite of claim 24, whereinthe elastic strand layer further comprises a meltblown web laminated tothe filaments.
 26. The nonwoven composite of claim 25, wherein themeltblown web contains the semi-crystalline polyolefin and the filamentscontain the thermoplastic elastomer.
 27. The nonwoven composite of claim19, wherein the elastic strand layer is also laminated to a secondnonwoven web facing.
 28. The nonwoven composite of claim 19, wherein thecomposite exhibits a heat shrinkage of about 40% or more after beingheated in water at 160° F. for 30 seconds to 1 minute.
 29. The nonwovencomposite of claim 19, wherein the composite exhibits a heat shrinkageof about 50% or more after being heated in water at 160° F. for 30seconds to 1 minute.
 30. The nonwoven composite of claim 19, wherein thecomposite exhibits a percent strain of about 40% or less when subjectedto a load of 2000 grams-force per 3 inches wide in the machine directionprior to heat activation.
 31. An absorbent article comprising thenonwoven composite of claim
 19. 32. The absorbent article of claim 33,further comprising a waistband formed from the nonwoven composite.
 33. Amethod for forming an absorbent article, the method comprising:fastening a nonwoven composite to one or more components of the article,the nonwoven composite comprising an elastic strand layer laminated to anonwoven web facing, the elastic strand layer comprising a plurality ofelastic strands and being formed from at least one thermoplasticelastomer and at least one semi-crystalline polyolefin, wherein thesemi-crystalline polyolefin constitutes from about 40 wt. % to about 95wt. % of the elastic strand layer and the thermoplastic elastomerconstitutes from about 5 wt. % to about 60 wt. % of the elastic strandlayer; heating the nonwoven composite; and allowing the nonwoven toretract, thereby increasing the stretchability of the composite.
 34. Themethod of claim 33, wherein the thermoplastic elastomer is selected fromthe group consisting of styrene-butadiene, styrene-isoprene,styrene-butadiene-styrene, styrene-isoprene-styrene,styrene-(ethylene-butylene), styrene-(ethylene-propylene),styrene-(ethylene-butylene)-styrene,styrene-(ethylene-propylene)-styrene,styrene-(ethylene-butylene)-styrene-(ethylene-butylene),styrene-(ethylene-propylene)-styrene-(ethylene-propylene), andstyrene-ethylene-(ethylene-propylene)-styrene, and combinations thereof.35. The method of claim 33, wherein the semi-crystalline polyolefin hasa density of about 0.91 grams per cubic centimeter or less and issingle-site catalyzed.
 36. The method of claim 33, wherein thesemi-crystalline polyolefin is an ethylene/α-olefin copolymer,propylene/α-olefin copolymer, or a combination thereof.
 37. The methodof claim 33, wherein the thermoplastic elastomer constitutes from about45 wt. % to about 90 wt. % of the elastic strand layer and thesemi-crystalline polyolefin constitutes from about 10 wt. % to about 55wt. % of the elastic strand layer.
 38. The method of claim 33, whereinthe strands are in the form of an array of continuous filaments.
 39. Themethod of claim 38, wherein the elastic strand layer further comprises ameltblown web laminated to the filaments.
 40. The method of claim 39,wherein the meltblown web contains the semi-crystalline polyolefin andthe filaments contain the thermoplastic elastomer.
 41. The method ofclaim 33, wherein an adhesive is used to fasten the composite.
 42. Themethod of claim 33, wherein the composite is heated at a temperature offrom about 50° C. to about 100° C.
 43. The method of claim 33, whereinthe composite is heated at a temperature of from about 70° C. to about80° C.
 44. The method of claim 33, wherein the retracted compositeexhibits a heat shrinkage of about 40% or more.
 45. The method of claim33, wherein the retracted composite exhibits a heat shrinkage of about50% or more.
 46. The method of claim 33, wherein prior to heating, thecomposite exhibits a percent strain of about 50% or less when subjectedto a load of 2000 grams-force per 3 inches wide in the machinedirection.
 47. The method of claim 33, wherein prior to heating, thecomposite exhibits a percent strain of about 40% or less when subjectedto a load of 2000 grams-force per 3 inches wide in the machinedirection.